The present invention is concerned with a method and an apparatus for the transportation of metal fibers which are produced in a magnetic field by thermal decomposition of metallic substances which are present in the magnetic field in gaseous phase.
In our copending application we have described a method and an apparatus for producing metal fibers in a magnetic field, according to which magnetic flux lines are generated which extend normal to a planar supporting surface located in an enclosed space. Metallic substances, for example carbonyls of metallic materials, are fed into the enclosed space for travel lengthwise of the flux lines and normal to the supporting surface. The space is heated to a decomposition temperature at which the substances undergo thermal decomposition and liberate metal atoms which agglomerate under the influence of the flux lines on the supporting surface and form thereon metal fibers projecting from the supporting surface in direction normal thereto. It is possible to produce iron fibers from iron carbonyls, or else to produce fibers of other metals from appropriate other metallic carbonyls. In fact, it is also possible to produce alloyed metal fibers from a mixture of different carbonyls or to produce metal fibers of one material which are coated with a plating of a different metal, all as described in our aformentioned copending application.
The transportation of the fibers being produced is effected in the prior art by a piston which is movable in the enclosed space, i.e. the reaction chamber in which the growth of the metal fibers during agglomeration on the supporting surface takes place. It has been found that a substantial portion of the metal fibers that grow does not form on the end face of the piston which forms the planar supporting surface, as intended, but insteads forms on the wall bounding the reaction chamber. The fibers are expelled from the reaction chamber in downward direction by operation of the piston and fall into a receptacle that is located beneath the reaction chamber.
The approach of the prior art is satisfactory for many applications. However, it cannot be used for producing strands of metal fibers of significant length, because the maximum fiber length that can be produced corresponds to the maximum length of the reaction chamber. Once this length has been reached, the fiber production must be interrupted and the fibers which have been produced in the reaction chamber must be expelled before a new production cycle can be begun. This means that a more or less continuous growth of fibers is not possible, and that it is simply impossible to produce fibers having any desired length. Of course, in many instances it is desirable that it should be possible to produce fibers having a greater length -- or even a very much greater length -- than the maximum length of the reaction chamber, quite aside from the fact that such continuous production avoids the frequent stopping of fiber production and expulsion of the finished fibers, and thus significantly increases the economy of the fiber-producing operation.